1. Field of the Invention
The invention pertains to waveguide assemblies such as may be used for mixers, detectors, or other such applications. More particularly, the invention concerns diode mounts for use in such waveguide assemblies.
2. Description of the Prior Art
The provision of a reliable diode mount in waveguide assemblies for cartridge type diodes and the like has long been a problem. Such diodes are generally constructed with an insulating cylindrical center portion and contacts on either end thereof. The active contact is also generally cylindrical but with a smaller diameter than the central body portion. The ground contact, however, was cylindrical but of a larger diameter than the central body portion and also having a further flange at the end of the base portion of the ground contact having still a greater diameter. Previous waveguide assemblies had mounts in which the diode was positioned and held in place by providing an aperture having a lip against which the flange could rest with a screw cap holding the flange against the lip. Connection to the active contact of the diode was provided through a contact rod or pin extending through an aperture in the opposite side of the waveguide. The position of the diode within the waveguide was determined entirely by the position of the lip against which the diode flange was secured. Unfortunately, as the aperture around the lip was necessarily of greater diameter than the base portion of the diode, there was an unavoidably large tolerance upon the lateral position of the diode within the mount.
In many applications, the longitudinal position of the diode as determined by the distance between the juncture of the active contact and central diode body and the wall of the waveguide adjacent the active contact is of critical importance in determining the effective inductance of the connections to the diode and the amount of coupling between waves in the waveguide and the diode. Because of manufacturing tolerances of both the diode base and central portion as well as tolerances on the distance between the lip holding the diode flange and the adjacent wall of the waveguide, the actual coupling in any one device was subject to wide variation. Moreover, because of the positioning problem in both lateral and longitudinal directions, additional resistance was introduced into both active and ground or base connections with the diode. Resistive losses, noise and RF leakage resulted.